**5. Seed production**

**4. Phytosanitary diagnosis**

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sanitary capacity to produce plant material in vitro.

**Common name Scientific name** Sugarcane scale *Aulascaspis tegalensis* Sugarcane leafhopper *Perkinsiella sacharicida* Sugarcane leafhopper *Pyrilla perpusilla* Spotted stalk borer *Chilo partellus* Sugarcane borer *Eldana saccharina* Purple stem borer moth *Sesamia inferens* Kenya mealybug *Planococcus kenyae* Giant moth borer *Castnia licoides*

Sugarcane downy mildew *Peronosclerospora sacchari*

Ratoon stunting disease *Leifsonia xyli* ssp. *xyli* Bacterial canker *Dickeya chrysanthemi* Bacterial wilt *Pantoea stewartii* Leaf scald of sugarcane *Xanthomonas albilineans* Virosis *Sugarcane Streak Virus* Virosis *Sugarcane Sereh virus* Sugarcane smut *Sphacelotheca erianthi* Sugarcane smut *Sphacelotheca macrospora* Sugarcane smut *Ustilago scitaminea*

**Table 2.** Pests and diseases which plant material produced *in vitro* must be free of.

Sugarcane gumming disease *Xanthomonas campestris pv. vasculorum*

Diseases represent one of the main factors that affect sugarcane production. Knowledge of phytosanitary status and the correct identification of phytopathogens are key to reducing losses due to diseases. In this regard, it is essential to carry out a phytosanitary diagnosis at an early stage to ensure the phytosanitary quality of the seedlings obtained in the laboratory. In many countries where sugarcane is an important part of the economy, plant health departments (PHDs) are responsible for certifying the procedures for obtaining pest- and diseasefree sugarcane vitroplants. The PHD determines the requirements necessary for accreditation of micropropagation laboratories engaged in in vitro culture of sugarcane, whose legal basis is determined based on Plant Health Laws. To obtain certification, a laboratory must meet a series of requirements that demonstrate technical competence, satisfactory infrastructure and

Accreditation of micropropagation laboratory: micropropagation laboratory should be accredited by an appropriate authority to ensure technical competence and satisfactory infrastructure.

> Seed production system comprises basic seed (primary seed), semicommercial seed (foundation or secondary seed) and commercial seed production.

> The unit area of the seed nursery should be approximately one-tenth of the area that is planned to be renewed each year in the commercial plantations. This plantation system is used because

the multiplication rate is around 1:10 (10 internodes/stem). Sugarcane stem used for seed production is composed of a series of internodes; each internode forms a new plant. Harvesting of each seed nursery takes place after 7–10 months of development, when the plants have the required physiological conditions to obtain seed (internodes). Physiological maturity also depends on the type of variety used. After the harvest, heat treatment of internodes helps to get rid of several diseases and pests. According to Jalaja et al. [23], for seed heat treatment, thermohydrotherapy is recommended. Internodes are immersed in water maintained at 50°C for 2–2.5 h. Fungicides and bactericides are mixed in hot water to eliminate diseases. Proper thermohydrotherapy and pesticide application ensure the eradication of diseases and insect pests. Each seed nursery is described below.

The basic seed nursery is established with vitroplants. The health status of the seeds should be adjusted to those of each country. In seed nurseries, two phytosanitary assessments should be carried out to detect off-types (mutations or varietal mixture) and to remove plants infected with diseases or pests: the first, at 4 months of age, and the second, immediately before the seed cut, at which time stem samples are randomly taken. With approximately 10,000 vitroplants/ha, with an average distance between furrow and plant of 1 × 1 m, it is possible to establish basic seed nurseries. However, the sowing density depends on the type of variety and cropping system.

The *semicommercial seed* nursery is planted with material from the basic seed or with material from the ratoon of another semicommercial seed nursery that has been heat treated. The area of this field is, in general, 10 times greater than that of the basic seed nursery; as in this one, at 4 months of age, a phytosanitary evaluation must be done, and at the time of the cut, samples must be taken for phytosanitary diagnosis.

The *commercial seed* nursery is established with material from the template or the first ratoon of a semicommercial seed nursery. The area is at least 10 times greater than that of the semicommercial seed nursery. Although in this case it is not necessary to thermally treat the material, it is recommended and the same phytosanitary evaluations should be carried out. This seed nursery must have a sanitary state like that presented by the semicommercial seed nursery.

seed should preferably be located near the commercial crop to minimize transportation costs and damage during transport. The sowing time of the commercial crop determines the time for establishing the seed nursery. This is because there are early, intermediate and late crop-cycle cultivars; other factors include the availability of irrigation or whether it is subject to a seasonal sowing calendar. The fields for this purpose must be chosen from among the best according to the physical and chemical conditions of the soil and water availability. For the commercial crop, a change of seed is required once every 4 or 5 years. This change of seed favors the repopulation of the plantation, as well the rejuvenation and health of the crop, which recovers its productive potential. It is important to mention that canes from the ratoon crop, however, should not be used for seed production [23]. This is because ratoon cropping involves growing a fresh crop from the suckers of the plant crop without replanting (second crop). Therefore, a decline in cane yield in successive ratoon crops has been reported; the causes for this decline are poor ratoon management, inherited differences in potential productivity and an increasing incidence of diseases which results in a gappy stand [24]. **Figure 4** summarizes the procedure for the seed production system to

**Figure 4.** Seed production system comprising basic seed (primary seed), foundation (secondary seed) and commercial

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seed production to obtain a commercial crop per unit area (UA).

In conclusion, commercial sugarcane micropropagation enables the massive multiplication of plants to obtain certified vitroplants and increase the sugarcane and sugar production per unit area. This technology helps farmers to enhance their crop productivity. In addition, a sugarcane micropropagation laboratory can be used for in vitro conservation of germplasm,

obtain a commercial crop.

In the seed production system, it is important that the growing area has some type of irrigation so that the seedlings do not suffer from stress. Seed has to have a high water content and good nutritional status. In addition, plants must receive all the care and practices required for good development. In order to ensure the proper development of each seed nursery, a technological package is required that includes crop fertilization and adequate pest, disease and weed control.

In each seed nursery, the following criteria must be met:


Finally, the commercial plantation comes from the template or ratoon of a certified commercial seed nursery. This area is 10 times greater than that of the commercial seed. Commercial

the multiplication rate is around 1:10 (10 internodes/stem). Sugarcane stem used for seed production is composed of a series of internodes; each internode forms a new plant. Harvesting of each seed nursery takes place after 7–10 months of development, when the plants have the required physiological conditions to obtain seed (internodes). Physiological maturity also depends on the type of variety used. After the harvest, heat treatment of internodes helps to get rid of several diseases and pests. According to Jalaja et al. [23], for seed heat treatment, thermohydrotherapy is recommended. Internodes are immersed in water maintained at 50°C for 2–2.5 h. Fungicides and bactericides are mixed in hot water to eliminate diseases. Proper thermohydrotherapy and pesticide application ensure the eradication of diseases and insect

The basic seed nursery is established with vitroplants. The health status of the seeds should be adjusted to those of each country. In seed nurseries, two phytosanitary assessments should be carried out to detect off-types (mutations or varietal mixture) and to remove plants infected with diseases or pests: the first, at 4 months of age, and the second, immediately before the seed cut, at which time stem samples are randomly taken. With approximately 10,000 vitroplants/ha, with an average distance between furrow and plant of 1 × 1 m, it is possible to establish basic seed nurseries. However, the sowing density depends on the type of variety

The *semicommercial seed* nursery is planted with material from the basic seed or with material from the ratoon of another semicommercial seed nursery that has been heat treated. The area of this field is, in general, 10 times greater than that of the basic seed nursery; as in this one, at 4 months of age, a phytosanitary evaluation must be done, and at the time of the cut, samples

The *commercial seed* nursery is established with material from the template or the first ratoon of a semicommercial seed nursery. The area is at least 10 times greater than that of the semicommercial seed nursery. Although in this case it is not necessary to thermally treat the material, it is recommended and the same phytosanitary evaluations should be carried out. This seed nursery must have a sanitary state like that presented by the semicommercial seed nursery. In the seed production system, it is important that the growing area has some type of irrigation so that the seedlings do not suffer from stress. Seed has to have a high water content and good nutritional status. In addition, plants must receive all the care and practices required for good development. In order to ensure the proper development of each seed nursery, a technological package is required that includes crop fertilization and adequate pest, disease and weed control.

• *Genetic purity of material*: high varietal purity, there being no more than one variety within

• *Genetic homogeneity*: clonal fidelity, identical plants without somaclonal variants (mutations).

Finally, the commercial plantation comes from the template or ratoon of a certified commercial seed nursery. This area is 10 times greater than that of the commercial seed. Commercial

pests. Each seed nursery is described below.

must be taken for phytosanitary diagnosis.

In each seed nursery, the following criteria must be met:

• *Plant health*: plants free of pests and diseases.

the seed nursery (varietal mixture).

and cropping system.

108 Sugarcane - Technology and Research

**Figure 4.** Seed production system comprising basic seed (primary seed), foundation (secondary seed) and commercial seed production to obtain a commercial crop per unit area (UA).

seed should preferably be located near the commercial crop to minimize transportation costs and damage during transport. The sowing time of the commercial crop determines the time for establishing the seed nursery. This is because there are early, intermediate and late crop-cycle cultivars; other factors include the availability of irrigation or whether it is subject to a seasonal sowing calendar. The fields for this purpose must be chosen from among the best according to the physical and chemical conditions of the soil and water availability. For the commercial crop, a change of seed is required once every 4 or 5 years. This change of seed favors the repopulation of the plantation, as well the rejuvenation and health of the crop, which recovers its productive potential. It is important to mention that canes from the ratoon crop, however, should not be used for seed production [23]. This is because ratoon cropping involves growing a fresh crop from the suckers of the plant crop without replanting (second crop). Therefore, a decline in cane yield in successive ratoon crops has been reported; the causes for this decline are poor ratoon management, inherited differences in potential productivity and an increasing incidence of diseases which results in a gappy stand [24]. **Figure 4** summarizes the procedure for the seed production system to obtain a commercial crop.

In conclusion, commercial sugarcane micropropagation enables the massive multiplication of plants to obtain certified vitroplants and increase the sugarcane and sugar production per unit area. This technology helps farmers to enhance their crop productivity. In addition, a sugarcane micropropagation laboratory can be used for in vitro conservation of germplasm, application of biotechnology for genetic improvement programs and easy transportation during exchange of in vitro plant material between countries.

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